The need for detecting and measuring gaseous components of the environment has been increased because of regulations which deal with clean air, clean water and a clean work place. Numerous devices have been produced to measure such gaseous components one of which operates on electrochemical principles. Many electrochemical processes for the determination of gaseous components are known in the art. See for example Advances in Electrochemistry and Electrochemical Engineering, Volume 10, (J. Wiley & Sons, 1976).
Of particular importance in any electrochemical detecting sensor is that it have high accuracy, good reproductability, high sensitivity to the gas sought to be measured and little interference from other gaseous components of the environment. And, in the case of threshold limiting value (TLV) measurements, a fast response time. Presently, most electrochemical sensors operate in an aqueous electrolyte, see for example U.S. Pat. Nos. 3,776,832 and 3,992,267. The most commonly used aqueous electrolytes incorporate solutions of sulfuric acid because of their insensitivity to carbon dioxide which is frequently present in gaseous mixtures. Unfortunately, aqueous electrolytes are restricted by the range of electrical potential at which water decomposes and by the high vapor pressure of water. Aqueous electrolytes also have a very high dielectric constant and, therefore, can generally dissolve more gas. However, such high dissolution rates also create various measurement distortions.
Various attempts have been made to construct electrochemical cells useful in measuring and detecting chlorine. Unfortunately, all of the electrodes selective to chlorine dissolve in the electrolyte medium in the presence of chlorine. It is presently believed that no one has successfully produced a primary continuous chlorine detecting electrochemical cell which operates utilizing an aqueous electrolyte which does not rely upon the destruction of the sensing electrode.
The present invention is directed to an electrochemical cell in which a substantially non-aqueous organic electrolyte is used to sense and measure chlorine gas. It is an object of the present invention to provide an electrochemical cell which is extremely accurate down to below about 1 part per million chlorine (the present TLV value), has a fast response time (less than 60 seconds) and has an extended useful life (over one year).